1. Field of the Invention
The present invention relates to shank portions of end mills among cutters such as end mills and reamers, and tool holders that chuck the shank portion of the end mill.
2. Background Art
Conventionally, shank portions of cutters such as end mills and reamers, and tool holders that chuck the shank portion of the cutter are proposed in, e.g., Japanese Unexamined Patent Publication Nos. 2002-346864 and 2001-87969 and Japanese Utility Model Publication No. H06-80509. Such conventional tool holders include two side lock bolts. The shank portion of the cutter basically has a circular cross section, and two flat surfaces are formed in the outer periphery of the shank portion. By fastening the two side lock bolts, the tip ends of the side lock bolts abut on the flat surfaces, respectively, whereby the shank portion of the cutter is chucked.